1. FIELD OF THE INVENTION
This invention relates to new and useful improvements in tubular well tools such as tool joints used in the drilling industry and provided with a hard metal coating to protect the joint against excessive wear and to prevent undue wear on the well casing.
1. BRIEF DISCUSSION OF THE PRIOR ART
For many years, tool joints used in the well drilling industry have been protected from excessive wear on their exterior surface by application of a band of hard metal thereon. It has been known that coarse-grained hard metal such as sintered tungsten carbide may be used and will provide a greater resistance to wear but may result in wear of the interior of the well casing. The wear from coarse-grained, sintered carbide has been blamed for expensive fishing jobs and junked holes. Other well tools, such as stabilizers, drill collars and connectors have had hard metal applied thereto and when used within well casing may cause accelerated wear on the casing.
In the co-pending application of Duane W. Wallace, Terry H. Mayo and Olen A. Curry, Ser. No. 607,014, filed Aug. 22, 1975, and assigned to the same assignee as this application, there is described an improved hard surfaced well tool in which a coarse-grained, sintered tungsten carbide is applied around a portion of the exterior surface of a well tool such as a tool joint and then coated with a softer material such as an alloy steel.